from the GNU version of the Collaborative International Dictionary of English

n. a member of the beat generation; a nonconformist in dress and behavior

Etymologies

Beat (Generation) + -nik.

(American Heritage® Dictionary of the English Language, Fourth Edition)

Coined by San Francisco columnist Herb Caen in 1958. From beat (generation) + cutesy or ironic use of the Slavic -nik (Russian: -ник). This suffix experienced a surge in English coinages for nicknames and diminutives after the 1957 Soviet launch of the Sputnik satellite. Compare jazznik. (Wiktionary)

Examples

In the collective mind of the general public, the word beatnik became synonymous with juvenile delinquent.

Still, it's worth recalling the nascent days of the counterculture, when "beatnik" was the opprobrious term applied to Sanders, Tuli Kupferberg and their ilk well before underground art turned psychedelic and the "summer of love" had hippies putting flowers in their hair.

The "Beat" generation was the brainchild of Jack Kerouac who despised the word "beatnik" and the distortion of his ideas. Kerouac was respecting of and devoted to the Catholic religion:

"It is because I am Beat, that is, I believe in beatitude and that God so loved the world that he gave his only begotten son to it... Who knows, but that the universe is not one vast sea of compassion actually, the veritable holy honey, beneath all this show of personality and cruelty?"

"I went one afternoon to the church of my childhood and had a vision of what I must have really meant with "Beat"... the vision of the word Beat as being to mean beatific... People began to call themselves beatniks, beats, jazzniks, bopniks, bugniks and finally I was called the "avatar" of all this."

--Kerouac article: "The Origins of the Beat Generation" (Playboy, June 1959).